The present invention generally relates to rotary air screens for filtering air flow to heat dissipating devices used for cooling functional elements of work machines such as harvesters for cotton, grains, and corn, construction machines, forestry machines, mining machines, and the like, and, more particularly, to a self cleaning, modular rotary air screen having improved operability, wear characteristics, and other advantages over known constructions.
Modern work machines, particularly agricultural harvesters for plants such as cotton, grains, and corn, are typically operated under hot, dry environmental conditions wherein considerable levels of dust, chaff, and straw and/or lint, are raised and are airborne in the vicinity of the machine. These machines include various functional elements, including, but not limited to, internal combustion engines and hydraulic systems, which are cooled by heat dissipating devices such as heat exchangers or radiators. Certain levels of air flow must be directed through the heat dissipation devices during various periods, to effect proper removal of heat therefrom, and to avoid overheating and premature breakdown and failure of the functional elements and the cooling systems. Often, the air flow requirements are greatest while the levels of airborne contaminants are high, creating an increased potential for the deposition and buildup of the contaminants in small interstices and passages in screens and grills covering and protecting the heat dissipating devices, and in the devices themselves, which can reduce the cooling efficiency thereof so as to require periodically stopping the operation of the machine and cleaning the heat dissipating devices and/or screens or grills.
Rotary air filters and screens having apparatus providing at least some self-cleaning capability so as to avoid manual cleaning requirements associated with the known fixed grills and screens, are known. Reference in this regard, Carnewal et al. U.S. Pat. No. 4,099,942 issued Jul. 11, 1978 to Sperry Rand Corporation, which discloses a rotary air filter utilizing a hollow perforated rotary structure having a generally unobstructed lengthwise inner surface, and a discharge opening in line therewith through which foreign material which enters the structure through the perforations can be discharged. It is also disclosed that the filter can include a brush positioned within the structure for brushing the inner perforated surface thereof when rotated. An observed shortcoming of rotary air filters of this type, however, is the requirement of relatively large perforations in the structure which can allow relatively large amounts of foreign material into the interior thereof, some of which foreign material can pass beyond the discharge structure and collect on the radiators, engine, and other functional elements to an undesirable extent.
Reference also, West et al. U.S. Pat. No. 3,837,149 issued Sep. 24, 1974, and Nelson et al. U.S. Pat. No. 4,906,262 issued Mar. 6, 1990, both to Deere and Company, which disclose rotary screens for an engine enclosure utilizing a partial vacuum chamber for suctioning material from the outer surface of the rotary screen, thereby providing a self-cleaning capability. An observed shortcoming of these devices, however, is the deposition of the suctioned material into the air flow over the engine so as to be capable of collecting in significant quantities on and around the engine.
Still other devices are known which scrape or plow material from rotary filters, as evidenced in Hursh U.S. Pat. No. 2,716,494 issued Aug. 30, 1955 to Lukens Steel company, and Cording et al. U.S. Pat. No. 2,636,612 issued Apr. 28, 1953 to the United States of America. However, the known scraper and plow devices are necessarily of rigid construction such that, if biased or urged against a filter screen to an effective extent, would likely stretch and deform the screen over time thus lessening the cleaning effect achieved. Also, such devices, if allowed to prolongedly contact a mesh screen or the like, can rub or wear through the screen, thus necessitating replacing or repairing the screen on a more frequent than desirable basis. Further, if the leading edge of the scraper or plow wears, it can form an edge that can tear and damage the filter screen. Some of the disclosed scrapers and plows also have relatively complex geometric shapes, making them costly to make.
With regard to replacement of the filter screens, reference Gerakios U.S. Pat. No. 5,360,541 issued Nov. 1, 1994 to Albany International Corp., which discloses a modular device for the ease of use and installation of filtration textiles, which utilizes individual removable sections for holding textile fabric that can be disassembled to allow replacing the fabric. However, this is in a context wherein the filter itself is a very large rotating table, on the order of 15 to 25 feet in diameter, which makes it desirable and economical to replace only the textile fabric. In contrast, the rotary air screens of the present invention are intended for filtering air flow to work machines, particularly, agricultural harvesters, and are typically less than one third the diameter of such rotary tables, making it more desirable to have wholly replaceable screen sections, as opposed to just replaceable screen fabric. Also, since the present rotary air screens are for work machines which have limited exterior spaces not used for other purposes, it is desirable to minimize the size of the rotary air screens.
Accordingly, it would be desirable to provide a rotary air screen for agricultural machines which more effectively filters air flow therethrough, without directing air containing contaminants and foreign material over the engine and other functional elements, which does not cause accelerated deformation or wear of the screen, which is simple and advantageous costwise, which is relatively compact, and otherwise overcomes the shortcomings of the various known filter and screen constructions discussed above.
According to one aspect of the invention, a rotary air screen assembly for a work machine which is rotatable about a rotational axis for filtering air entering an air inlet of the work machine is disclosed. The screen assembly has an axially facing screen surface including an outer circumferential edge disposed around the rotational axis in radially spaced relation thereto. An elongate brush having bristles disposed along a longitudinal extent thereof is in contact with the axially facing screen surface for brushing collected material and contaminants therefrom, the longitudinal extent or axis of the brush forming a chord of the outer circumferential edge spaced a distance from the rotational axis, or being skewed relative to the rotational axis, such that when the screen is rotated about the rotational axis in a predetermined direction, a force is imparted to the collected material and contaminants by the bristles of the brush sufficient to move the collected material and contaminants radially outwardly past the circumferential edge and off of the axially facing screen surface.
According to another aspect of the invention, the screen surface can include a plurality of screen panels removably disposed around a center hub through which the rotational axis extends, each of the screen panels including a peripheral frame defining an opening therethrough, and a screen fabric permanently attached to the frame around the opening in covering relation thereto, allowing quickly and easily replacing the panels as they wear or are damaged. The preferred screen panels form a substantially continuous screen surface, and the screen fabric preferably includes openings having an average size of from about 100 to about 900 microns, which is substantially smaller than the size of screen openings of screen fabrics previously known to be used.